Jason is 20 and Mandy is 15.
Let j be Jason's age and m be Mandy's age.
Then j+m=35. Solving this for j, we have
j = 35 - m
Jason's age 10 years ago can be represented by j-10 and Mandy's age 10 years ago can be represented by m-10:
(j-10)=2(m-10)
Using the distributive property, we have
j-10=2*m-2*10
j-10=2m-20
Substituting our value for j from the first equation in, we have
35-m-10 = 2m-20
25-m = 2m-20
Add m to both sides:
25-m+m = 2m-20+m
25=3m-20
Add 20 to both sides:
25+20=3m-20+20
45=3m
Divide both sides by 3:
45/3 = 3m/3
15=m
Mandy is 15.
Jason is 35-15=20.
